Theory of magneto-mechanical systems as applied to telephone receivers and similar structures

A sufficiently general theory of magnetic vibratory apparatus is deduced to cover all practical problems in the operation of the various types of telephone receivers as transformers of electrical into acoustical or acoustical into electrical energy. A set of linear equations is derived relating currents in windings, mounted either on a stationary support (pole piece) or on the moving part (diaphragm or armature), and the motion of the moving part. The effect of eddy currents is included by treating each eddy circulation as a circuit. From the equations derived, it is possible by simple algebraic processes to calculate the effect of eddy currents and diaphragm or armature motion in terms of the constants or impedances of the system. By making certain constants of the equations either infinite or zero the different receiver types are represented including (1) simple receiver without eddy currents, (2) receiver with eddy currents in the pole pieces, (8) receiver with eddy currents in the diaphragm, (4) receiver with eddy currents in both pole pieces and diaphragm, (5) receiver with the driving coil on the diaphragm, and (6) receiver with non-magnetic but conducting diaphragm.